What dairy farmers should know about genetic selection

Transcription

1 52nd Florida Dairy Production Conference 9 Gainesville, FL, April 6, 2016 Francisco Peñagaricano Department of Animal Sciences University of Florida Genetic selection decisions one of the most important decisions that a dairy producer frequently makes represents a great opportunity to improve the profitability of the dairy production enterprise Changes achieved through selection are: cumulative permanent cost-effective Phenotypic Trend Genetic Trend OUTLINE Introduction Selection for multiple traits Take home messages Dairy bulls are genetically evaluated for several traits Production traits Fertility traits Health traits Type traits This information is regularly compiled and published as sire summaries

2 52nd Florida Dairy Production Conference 10 Gainesville, FL, April 6, 2016 Sire summaries There are at least three key concepts that appear in the sire summaries that we should consider in order to make proper sire selection decisions Predicted Transmitting Ability (PTA; a measure of the genetic merit of the bull) Reliability (REL or %R; a measure of the degree of confidence in the PTA of the bull) Percentile Rank (a measure of the rank of the bull within the evaluated population) Predicted Transmitting Ability (PTA) PTAs are exceptional tools for comparing and ranking available bulls the difference between the PTAs of two bulls is an estimate of the difference we expect to observe in the performance of their progeny 7HO11351 Supersire +71 PTA Protein 7HO11123 Wright +17 PTA Protein Supersire daughters will produce 54 more pounds of protein than Wright daughters Predicted Transmitting Ability (PTA) genetic prediction that we should always use when making sire selection decisions estimate of the relative genetic superiority that a bull will pass to its offspring PTA value on one animal has no special meaning because PTA is not an absolute value PTAs are exceptional tools for comparing and ranking available bulls Predicted Transmitting Ability (PTA) PTAs are exceptional tools for comparing and ranking available bulls the difference between the PTAs of two bulls is an estimate of the difference we expect to observe in the performance of their progeny 7HO11351 Supersire +7.0 PTA Productive Life 7HO11123 Wright +8.6 PTA Productive Life Wright daughters will survive 1.6 more months than Supersire daughters

3 52nd Florida Dairy Production Conference 11 Gainesville, FL, April 6, 2016 Reliability (REL %R) it measures the accuracy or degree of confidence in the PTA it is expressed as percentages and range from 1 to 99 REL is a function of the heritability of the trait and the amount of information available if heritability and the amount of information increase, then REL also increases bull has a more reliable PTA for protein yield than for daughter pregnancy rate because protein yield has higher heritability bull with many daughters has a more reliable PTA for any given trait than a bull with no or just few daughters Reliability (REL %R) currently, the number of young genomic-tested bulls (G) available in the marketplace far exceeds the number of progeny-tested bulls (A) young genomic-tested bulls have in average higher predicted genetic merits; as a counterpart, they have lower reliabilities the best strategy for managing the risk associated with lower reliabilities of genomic-tested bulls is to increase the number of young bulls that are used: No. genomic-tested bulls REL (average) genetic merit Reliability (REL %R) it measures the accuracy or degree of confidence in the PTA although we should not select or exclude potential sires based only on reliability, we can use REL values as a guide to decide how intense we want to use a bull. we might choose to purchase: 120 units of semen from a progeny-tested bull with 95% REL OR 20 units of semen from each of 6 different young genomic-tested bulls with 70% REL (young bulls with better genetic merit than the progeny-tested bull) Percentile Rank tables or graphs of PTA distributions useful information regarding the rank or position of a bull within the population evaluated interpretation: if a bull ranks for a given trait at the 95th percentile, this means that the bull is genetically superior to 95 percent of all the evaluated bulls of its breed.

4 52nd Florida Dairy Production Conference 12 Gainesville, FL, April 6, 2016 Percentile Rank useful information regarding the rank or position of a bull within the population evaluated Percentile PY PL DPR 99th (TOP 01%) th (TOP 05%) th (TOP 10%) th (TOP 20%) th (TOP 30%) th (TOP 50%) [1] Twister ranks in the top 30% for PY [2] Twister ranks in the top 5% for PL [3] Twister ranks in the top 30% for DPR Twister +24 PTA PY +6.9 PTA PL +1.7 PTA DPR Sire selection for multiple traits there are a large number of traits, including production traits (such as milk yield and milk composition) and fitness traits (such as longevity, fertility, udder health, and calving ability) that directly impact the profitability of the dairy production enterprise different methods for selecting sires considering multiple traits of economic importance Percentile Rank Independent Culling or Rejection Levels first choose minimum standards or cut-off values for each of the traits undergoing selection then select only those bulls that meet simultaneously all these criteria we might decide that we will only use bulls with PTAs that are at least: +31 for protein yield, +4.3 for productive life, and +2.5 for daughter pregnancy rate

5 52nd Florida Dairy Production Conference 13 Gainesville, FL, April 6, 2016 Independent Culling or Rejection Levels simple method that allows to select simultaneously for multiple traits using simple rules this method has some important limitations: 1. minimum standards are in general chosen arbitrarily without using any formal approach 2. these values may vary over time due to genetic progress and changes in the genetic base: cut-off values that are appropriate today may be too liberal or too restrictive in the near future 3. this method ignores the genetic relationships between traits of interest this impacts the efficiency of selection when we select for traits that are genetically correlated 4. the effectiveness of the method decreases as the number of traits under selection increases fewer bulls meet all the criteria, and these bulls are only marginally superior for each trait Economic Selection Index Lifetime Net Merit (NM$), Cheese Merit (CM$), Fluid Merit (FM$), and Grazing Merit (GM$) these indices consider simultaneously: production traits (including milk, fat, and protein yield) female fertility traits (including daughter pregnancy rate, heifer conception rate, and cow conception rate) productive life somatic cell score functional type traits (three composite traits, including udder, feet and legs, and body size) calving ability Economic Selection Index better approach for selecting sires considering multiple traits combines multiple traits into a single value, greatly facilitating the identification of the best bulls individual traits are weighted based on relevant genetic information and economic importance these economic weights are based on current prices for both inputs (e.g., feed and veterinary costs) and outputs (e.g., milk prices) of a dairy farm these values are updated regularly to reflect current trends in the price of feed and milk Economic Selection Indices: relative weights Lifetime Net Merit (NM$), Cheese Merit (CM$), Fluid Merit (FM$), and Grazing Merit (GM$) Trait NM$ CM$ FM$ GM$ Protein Fat Milk PL SCS Udder Feet/Legs Body size DPR HCR CCR CA$ source:

6 52nd Florida Dairy Production Conference 14 Gainesville, FL, April 6, 2016 Lifetime Net Merit Index (NM$) probably the most popular index represents the most appropriate breeding goal for the vast majority of US dairy farmers Trait NM$ Protein 20 Protein and fat yield receive the highest weights (20% and 22%) Fat 22 Milk -1 Productive life has the highest weight (19%) among the fitness traits PL 19 Female fertility traits receive a relative weight of 10% SCS -7 Udder 8 Feet/Legs 3 Overall, NM$ has relative weights of Body size -5 43% for production traits DPR 7 HCR 2 41% for health and fertility traits CCR 1 16% for functional type traits CA$ 5 Alternative indices Three indices are available for producers with special milk markets or production systems Trait NM$ CM$ FM$ GM$ Protein Fat Milk PL SCS Udder Feet/Legs Body size DPR HCR CCR CA$ Cheese Merit Index (CM$) For dairy farmers who are paid mainly for milk components Lifetime Net Merit Index (NM$) Correlations of PTAs between NM$ and some important traits Traits MY PY FY PL SCS DPR NM$ NM$ is highly correlated with protein and fat yield, and also with productive life Milk is positively correlated with protein and fat yield, and hence, it is also correlated with NM$ High NM$ values are associated with low somatic cell counts High NM$ values are associated with high daughter pregnancy rates Alternative indices Three indices are available for producers with special milk markets or production systems Trait NM$ CM$ FM$ GM$ Protein Fat Milk PL SCS Udder Feet/Legs Body size DPR HCR CCR CA$ Fluid Merit Index (FM$) For dairy farmers who are paid mainly for milk volume

7 52nd Florida Dairy Production Conference 15 Gainesville, FL, April 6, 2016 Alternative indices Three indices are available for producers with special milk markets or production systems Trait NM$ CM$ FM$ GM$ Protein Fat Milk PL SCS Udder Feet/Legs Body size DPR HCR CCR CA$ Contact Information: Phone: (352) fpenagaricano@ufl.edu Website: fpenagaricano-lab.org Thanks for your attention! Grazing Merit Index (FM$) pasture-based dairy producers Take Home Messages Key points to consider when making selection decisions Sire selection represents a great opportunity to improve the profitability of the dairy enterprise If breeding for profit is not your objective then I wish you all the very best with your hobby Sire selection decisions should be based on PTA information The selection of sires considering multiple traits should be based on economic selection indices The percentile rank helps to see how genetically superior the bull in question is compared with the rest of the available bulls The reliability should be used for managing the risk associated with the imprecision in the estimate of the genetic merit

8 NOTES 52nd Florida Dairy Production Conference 16 Gainesville, FL, April 6, 2016